1. Technical Field
The present invention relates to a radiation-curable ink composition and relates to an ink jet recording process using the same and a recorded matter.
2. Related Art
Recently, radiation-curable inks, which are cured by irradiation with ultraviolet rays, electron beams, or other radiation, have been being developed. Such radiation-curable inks are quick-drying and, therefore, can achieve recording without bleeding on a non-absorbing medium that does not absorb or hardly absorb ink, such as plastics, glass, or coated paper. The radiation-curable inks are constituted of polymerizable monomers, polymerization initiators, pigments, and other additives.
Incidentally, in a case that a recorded matter in which an image is recorded on a recording medium having flexibility, such as a polyethylene terephthalate resin or a vinyl chloride resin, is attached to goods having a curved surface, such as a car body, since the recorded matter is usually used in an elongated state, it is desirable that the image recorded on the recording medium have a degree of elongation of 100% or more not to cause cracking or peeling-off when it is stretched and also have durability that can withstand such as a degree of elongation.
In order to record a flexible image having a degree of elongation of 100% or more, an existing radiation-curable ink contains a polymerizable monomer such as long-chain alkyl acrylate, phenoxyethyl acrylate, or an ethylene oxide adduct of phenoxyethyl acrylate (for example, see JP-A-2006-199924, JP-A-2007-131754, and JP-A-2008-7687).
However, even in an image recorded using a radiation-curable ink containing the above-described specific polymerizable monomer, if the image is held in an elongated state (for example, a degree of elongation of 100%) together with the recording medium, cracking occurs within several hours, and, further, the image peels off from the recording medium. In addition, the toughness of the recorded image is insufficient, and the abrasion resistance is inferior.
Furthermore, in existing radiation-curable ink compositions, ethylene glycol bifunctional monomers or propylene glycol bifunctional monomers are widely used as crosslinking agents. However, some images recorded using radiation-curable inks containing these bifunctional monomers as crosslinking agents are inferior in weather resistance.